NET-PD -LSI is a trial conducted by the NET-PD network whose aim is to investigate the primary hypotheses that daily administration of creatine (10 gm a day) is more effective than placebo in slowing clinical decline in Parkinson disease (PD) between baseline and a five-year follow-up visit. There are no current therapies that slow down PD, a disease that affects more than half a million Americans and causes increasing disability, diminished quality of life and increased health care costs. The study is designed as a phase 3, multi-center, double blind, placebo controlled trial tested against the background of dopaminergic therapy (dopamine agonists and levodopa) and best PD care. The primary outcome is a global measure of clinical decline, comprised of 5 measures covering motor function, cognition, disability and quality of life. LS1 uses a novel design that permits less data collection between the two main time points (baseline and end-of trial), with incorporation of telephone interviews and reduction of in-person visits. Last follow up visits are planned between June 2014 and May 2015. Participants are kept in study and continue receiving study drug until the last participant completes five years of taking it. Participants whose study drug has been withdrawn are encouraged to continue being followed up, with the possibility of future re-challenge. The study has completed enrollment and has shifted effort to participant retention. A Recruitment and Retention Committee is engaged in efforts to assist sites in the process of retention. Central Coordination Center maintains regular contact with each site, monitors performance, reviews adverse events, administers and maintains data capture, holds telephone conferences and in-person annual meetings, and promotes publication of results via working group committees. As one of the participating centers, the University of Miami plans to continue the efforts of retaining 32 participants. The center will continue providing data on clinical cours and retention including its large subgroup comprised of an under-represented minority (Hispanics).